a. Field of the Invention
This invention relates to lenses and more particularly, to an ophthalmic lens construction which can be made without grinding and polishing.
B. Prior Art
Most manufacturers of ophthalmic lenses produce a large number of lenses because of the wide variances in ophthalmic corrections that are required. For example, meniscus or spherical lenses are made with powers between -7.00D and +7.00D, usually in 0.25D steps. Toric lenses, i.e. cylindrical lenses, combine a cylindrical element of 4.00D, usually in 0.25D steps with the same range of spherical power mentioned above. Thus, it may be seen that a large number of corrections faces ophthalmic lens manufacturers. In addition to the above-mentioned corrections, prismatic, bifocal, multifocal and tints may add further variety to the manufacturing process.
Ophthalmic practitioners usually send an order to a factory where prescription lenses may be ground and polished to the desired correction. It has been a long standing desire of such practitioners to be able to construct lenses in their own laboratories without ordering corrective lenses from a distant factory.
It has long been known that a desired degree of correction for a lens may be accomplished by combining, such as by bonding together, several stock lenses. Moreover, it has been known that the thickness of thick ophthalmic lenses may be reduced by means of Fresnel reduction, see for example British Pat. No. 1,154,360, granted Feb. 1, 1967 and incorporated by reference herein. The method of making reduced thickness lenses of the Fresnel type is the subject of U.S. Pat. No. 3,827,798 granted Aug. 6, 1974 to Luis Alvarez, which patent is also incorporated by reference herein.
It is known that polarizing lenses may be made of lenticular layers of different indices of refraction, see for example U.S. Pat. Nos. 3,213,753 and 3,522,985.
It is an object of my invention to devise a relatively thin ophthalmic lens which may be made in a small laboratory without grinding and polishing.